Obama and Medvedev pledged today to reduce their nation's nuclear stockpiles by a third, from 2,200 deployed warheads for each country to 1,550 over seven years. The treaty signing comes after more than a year of intense negotiations and several missed deadlines between the United States and Russia.
The scene in Prague was one of cooperation between the United States and Russia but back home, the Obama administration may face a challenge getting this treaty through the Senate.
The agreement requires the support of two-thirds of the Senate (67 votes) for ratification. Given the Democrat's 59-seat majority, it looks as if they will need at least eight Republicans to get on board to make the treaty official.
Senate Republican leadership sources say the minority's leaders don't have a firm position because they have not been consulted in any substantive way about the treaty by the Obama administration beyond some minor discussions.
This week the White House has been consistently emphasizing that past Senate votes on nuclear arms reduction treaties passed with overwhelming bipartisan support.
"If you look back at previous nuclear reduction treaties in the late '80s, the early '90s, and even as late at 2003, these are documents that enjoy vast bipartisan majorities -- votes in the '90s," White House press secretary Robert Gibbs told reporters on Air Force One en route to the Czech Republic. "We are hopeful that reducing the threat of nuclear weapons remains a priority for both parties."
Earlier today in Prague, Obama expressed confidence that the treaty would be ratified.
"I am actually quite confident that Democrats and Republicans in the United States Senate having reviewed this will see that the United States has preserved its core national security interests," he said. "That it is maintaining a safe and secure and effective nuclear deterrent but that we are beginning to once again move forward leaving Cold War behind to address new challenges in new ways."
But in the interview with ABC News' Stephanopoulos, Obama would not declare definitely that he knew how the issue would play out in the Senate.
"I've now been in Washington for long enough that for me to say I have no doubt how the Senate operates would be foolish," he said.
Obama singled out the ranking Republican on the Senate Foreign Relations Committee, Sen. Dick Lugar, R-Ind., as a Republican leader that he has confidence in based on their work together on this issue when Obama was in the Senate.
Lugar's view, which will carry some weight among his fellow Republicans, is said to be "favorable," a Lugar aide tells ABC News, but he needs to do "due diligence" and go through the process of reading the treaty and its annexes, which will take some time.
Obama told Stephanopoulos that his administration is "absolutely confident" that the new nuclear treaty will in no way impede the U.S. ability to move forward on a missile defense program.
"It is going to be contingent and developing based on our threat assessments," the president said.
"If for example, we are able to create a situation where Iran is no longer posing us a threat in terms of intercontinental ballistic missiles, then it may be that our missile defense configuration is able to be scaled back in a way that doesn't threaten Russia," he told Stephanopoulos.